


Temptation

by FullOfBoredom



Category: Undertale (Video Game)
Genre: Breastfeeding, Ecto-Genitalia (Undertale), Lingerie, M/M, Past Swapcest, Pregnancy, rottenberry
Language: English
Status: Completed
Published: 2021-01-24
Updated: 2021-01-24
Packaged: 2021-03-16 02:55:44
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,337
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28949286
Author URL: https://archiveofourown.org/users/FullOfBoredom/pseuds/FullOfBoredom
Summary: Blue was tired.He wasn’t used to feeling so run down, but after cleaning the house, doing laundry, and making food, Blue couldn’t deny wanting to lay down and take a nap. It probably was in large part due to the souling inside his body.
Relationships: Papyrus/Sans (Undertale), Sans/Sans (Undertale)
Comments: 2
Kudos: 57





	Temptation

Blue was _tired_.

He wasn’t used to feeling so run down, but after cleaning the house, doing laundry, and making food, Blue couldn’t deny wanting to lay down and take a nap. It probably was in large part due to the souling inside his body. 

Skeleton pregnancies didn’t last as long as human ones, but that didn’t mean they weren’t hard on the body. Blue was in the last stretch of the pregnancy, quite large, and very exhausted from supplying so much energy to the tiny soul inside his body. He had a sizable bump by now. Blue rubbed it gently while sitting down, through his very comfy sweater he half lived in right now, turning in his boots for slippers, seeking relief from the constant ache from being much heavier on his feet. It also didn’t help that he had boobs now, ecto body creating a place to keep breast milk for the upcoming baby.

It would help if Stretch supported him a little. It was like he’d vanished from the house. Stretch had been kind of supportive early on, but with each passing month, he became more and more distant. 

It hurt. This wasn’t a planned baby, but they knew it was a risk and could happen at any time. 

It was also physically hurting him, because the lack of both parents being nearby at all times meant the baby sucked a lot of energy from just Blue, and it was creating problems that wouldn’t exist if Blue wasn’t alone all the time. 

Stretch had been coming home most nights from Muffet’s now and Blue had had enough. Honestly, all he was waiting for was the birth and the baby to hopefully fix whatever was freaking out Stretch. For now, he just settled in and tried to be comfy.

He pulled out his phone to call his best friend, Black.

“Blue, I’m very busy at the moment. Is this an emergency?” He picked up immediately, but didn’t waste any time.

“No. I’m sorry.”

“Don’t be. I’ll call you after I’m done.” And he hung up. His body gurgled, he waddled to the kitchen to fix up a snack.

 _“Do you really need all of that?”_ Blue froze mid-walk. Stretch had said that a month ago, commenting on all the food Blue was eating. It sucked, he felt fine, the doctor said it was fine, but he returned forlornly to the sofa, sad and hungry. He turned on the TV. Napstablook’s cooking show. He turned it off.

When he closed his eyes and laid his head back, he could hear all the other comments Stretch had been slipping into their conversations.

_It’s not that hard._

_Single monsters manage fine._

_You’ve gotten…big._

_Thinking about you that way is weird._

_I didn’t ask for this._

Blue’s pregnancy was miserable, not able to enjoy the small things like the soul’s little jostles of joy when it was near Stretch because Stretch didn’t love them back. He tried not to think too hard about whether he didn’t love Blue back either, but following that train of thought only led to sadness.

The phone rang.

“Blue, I’ve got some time. How are you?” Black’s voice came in clear and crisp, clothes rustling from his movement in the background.

“Tired. So very tired. I need some best friend time, when’s a good time for you?” Blue kept one hand on his belly, hoping the souling couldn’t feel his turmoil.

“I have the evening free if you’re not spending it with your _boyfriend_.” Black’s words came through with a sneer. He didn’t approve of Stretch’s treatment of Blue, but Blue cut him a lot of slack considering the suddenness of it all. 

“I doubt he’ll be coming home. He hasn’t in days.” Blue’s little energy he had left disappeared. It felt worse to acknowledge out loud.

“Then I’ll be by after work. Be dressed to leave, we’ll go back to my place. Wallowing at home won’t solve anything.” Another muffled voice drifted into the receiver. “I must return to my duties. See you later?”

“Yeah. Thanks Black.” Another hang up. Black was short and to the point, but he had never left Blue hanging. The idea of getting dressed to get out exhausted him though.

He hauled himself up, and made his way up the stairs.

His closet was…lacking. Almost nothing fit anymore, at least as far as tops. He put on a loose sweater that bunched up around his huge top half. The bras were all unattractive plain colors, meant to protect against leaking milk on himself. Blue looked in the mirror.

A fat ugly mess who got knocked up by someone who only wanted him for fun, not forever.

Black found him crying hysterically when he opened the door.

“What’s wrong Blue?” He pulled him into a hug. Blue was so big that Black couldn’t pull him close enough to cry on his shoulder. Black angled the hug, rubbing Blue’s back while he laid on Black’s shoulder.

“I’m an ugly fat skeleton!” Blue sobbed but Black was accustomed to this by now. Blue’s pregnancy was rough, Black produced a pack of tissues from a pocket.

“That’s nonsense and you know it.” Black soothed, but didn’t allow for self pity. “You are carrying a child. And you are very attractive.” He smoothed out Blue’s sweater, running a hand over his stomach. “Now wash your face and we’ll leave.”

Blue and Black ended up at the mall. Not Blue’s first choice after the self esteem meltdown, but it was fun to go out with Black. They had some nice cream (well Blue did), looked at different baby clothes, and window shopped for Black. It was just a fun day out on the town. Blue’s energy was waning, baby bouncing around inside his stomach, about to ask to go home when Black stopped short at a window display.

“Black?”

The display was in front of a prominent undergarment shop. A thin lace bra, small nipple window on each side. Thin ribbons linked down along the sides to a thin pair of panties, half lace, half sheer. They linked even further down to thigh high fishnet leggings. Blue admired the look, but not nearly as much as his best friend. Black vanished inside, Blue hesitant to follow. 

Blue needn’t worry though. Black came out very quickly with a bag.

“Sorry Blue. It seems perfect for what I wanted.” He smiled at Blue. “Let’s return to my home. I’m sure you’re tired.” Blue smiled back, but definitely unhappy.

“Pretty please. My feet are killing me. Also, your place?” They made their way out, Blue holding his back from the strain. Black placed a hand on Blue’s back as well.

“I figured you didn’t want to spend the evening alone. I also planned on making dinner.” Black let him back towards his own apartment, Blue following without any complaint. Being alone again sounded awful. He didn’t bother to check the messages Stretch anymore. It was all the same, the same excuse, the same place, the same late return home. Black’s home felt more like his home.

They swept in around dinner time. Black led him to a comfortable chair, before heading into the kitchen. Oddly, he made a pit stop to the washing machine.

Blue sighed happily from the scent of Black’s home. Lit candles decorated the living room, the tidy apartment free of clutter and dust. Black cooked the best out of everyone he knew, but he didn’t often come over anymore. Stretch didn’t like how much time he spent with Black before the pregnancy, but he hadn’t said much after. He rubbed his belly, the souling pulsing pleasantly. Blue closed his eyes, forgetting about Stretch, and just considering how cute his future baby would be.

A second hand covered his.

“I can’t wait to meet them.” Black grinned slyly, but Blue just hummed in agreement. “Food is ready, chicken alfredo.”

“You DO love me.” Blue stuck his tongue out. “My favorite.” He smiled so wide. Time with Black really healed his soul from troubles. Two plates were already filled and sitting on the table, Black’s plate with a glass of wine, Blue’s with juice. Blue did notice that his plate had a lot more than Black’s.

“Bon appetit.” Black toasted him over the table, and Blue raised his cup as well. 

The food was amazing, as usual. Distant thoughts of Stretch’s _do you need all that_ echoed in his mind, but he didn’t want to waste what Black had given him. It certainly kept him from asking for seconds though. 

Speaking of Black, his plate was similarly clean, but he was staring at Blue over the table, swirling his mostly empty glass. His gaze was fond, gesturing to the extra portions on the stove.

“You can have more, I did make plenty.” His eyes trailed over Blue’s body. Blue blushed and looked away.

“I don’t need anymore.” Blue gave a non-convincing smile. Black frowned.

“But you want more.” Black raised a brow. “Why would you stop eating if you’re not satisfied?” Blue sensed he knew the answer already, just didn’t like it.

“I’m…big enough Black.” Blue tried to hide in his sweater. “I don’t need it.”

Black glared at Blue, but Blue could read who he wanted to glare at.

“Did Stretch tell you that?” Black crossed his arms, leaning back in his chair. “I understand not stuffing yourself for the sake of it. But you’re clearly drained from his lack of soul magic, and are still very hungry. That asshole’s opinion on your body stopped mattering when he stopped caring about you and the baby.”

Blue curled in on himself, as far as he could with such a large bump.

“He hates me Black. He hasn’t slept in our bed in weeks. I’m a bad boyfriend. I’m gunna be a bad mom.” Blue’s emotions surged up, making him cry again. He felt hands on his face, gently wiping the tears away.

“You’re wonderful. He’s the one who’s trash.” Black switched to holding Blue’s stomach. “He got so very lucky and walked away for something fucking absurd.”

“You think he’s lucky?” Blue looked down at Black. Black pressed a kiss to his covered stomach.

“Very.”

Blue blushed so bright blue, his face glowed, but he still felt unsure. 

“But I’m so…” He gestured to the big bump, the boobs, the frumpy loose sweater that drowned him. Black stood decisively. He stalked away, but reappeared before Blue panicked about his words. He pressed something into his hands.

“If you want to see how lucky I believed Stretch to be, come to my room in this. If you choose to stay alone in the guest room, I will not speak of this again.” Black kissed his forehead before turning around to cover the leftovers for fridge storage. Blue retreated to the guest room quickly and quietly, before he could think too much. Black’s offer was unclear, up until he looked at what he was holding.

The lacy lingerie. In his size.

This! Would barely fit! The ribbons would be pulled taut around his belly. His boobs were heavy and full, they could wet the bra and anything nearby from the nipple windows. It’d look ridiculous on him!

But Black had asked. Even if he decided that Blue looked stupid in this, Black would scrap the clothes and do what he wanted anyway.

Did he want Black to do what he wanted? He was pregnant with Stretch’s baby.

But Stretch hadn’t even looked at him. He ignored him entirely. Clearly he wasn’t wanted there. He slid on the clothes, blue ecto body straining the bra, ribbons tightly wrapped around the sides of his pregnant belly. The panties barely held him in, half his labia ready to burst from the confines. The mirror made him want to cry. He walked directly over to Black’s room before he could change his mind.

Black was reading on his bed when Blue walked in. Casually perusing like he hadn’t asked Blue to show up in this ridiculous outfit for him. When he glanced up, he snapped the book shut without saving his place.

“You do know what I intend to do to you, correct?” Black’s eyes locked with his, sliding off the bed without breaking the gaze.

“The outfit gave me a good guess.” Blue felt hypnotized, Black still approaching.

“And you accept this? What doing this would mean?” Black reached him, cupping his face with a single hand, the other settling gently on the side of his ecto belly. Blue could barely breathe.

“Yes.” Blue watched as Black slowly descended, eyes slipping shut just before impact.

Black’s purple tongue licked into his mouth instantly. Blue whined into the kiss, taking Black’s intense claim, tasting the intruder as he explored every crevice. His body shuddered hard. He hadn’t been touched or touched himself in a long time.

“Beautiful, amazing, perfect. And if I have my way, mine.” Black took a breast in one hand, massaging the soft supple ecto, taking a nipple in his mouth on the other.

“Blaaaack!” Blue whined shimmying his hips from the sensations. Each of his nipples sent shocks of pleasure into his body, like he’d never been touched there before. Also, to his mortification, they began to leak milk. “Oh, god, I’m sorry, I-”

Black sucked hard on the nipple in his mouth. Blue almost collapsed. Black then switched, licking up the excess before sucking on the other. 

Blue clutched the back of Black’s skull, not holding him there but holding BLUE there.

When Black came back up, taking Blue’s mouth again, he could taste the milk on his tongue.

“Don’t apologize.” He kissed him, repeatedly. Black traced his hands over his stomach, softly trailing his fingers over the bump. “If anything, I apologize for taking some from the baby.” Black slipped his hands under the ribbons wrapped around his stomach. “What a lovely gift.”

Blue kissed him hard, fisting his hands in Black’s shirt. Black slipped a hand between them, right into those see through panties. Blue broke the kiss with a gasp.

“That’s my good boy.” Black held Blue close while he shivered and cried out. His hand kept working at him. “You’ve been so neglected, look how sensitive you’ve gotten.”

“Please help me Black.” Black guided him to the bed, talented fingers keeping pace. Blue sat back, legs spread for that attentive hand.

“Of course Blue, I just need something first.” Black popped open his belt buckle. Blue’s eyes were half rolled back in his head. His mouth kept moving and moaning, trying to find the words to respond, but couldn’t pick any until he heard the subtle drop of clothes to the floor.

“Anything you want.” Black withdrew his hand to Blue’s whine, but when he finally focused, he could see Black was down to a shirt and rapidly removing that. He stooped down to take another taste of those delicious breasts he’d enjoyed so thoroughly the first time.

“Let me claim you. I want this gorgeous pussy to myself.” Blue’s body arched up at the thought, Black grinning at him before returning to his previous job of working Blue into a frenzy.

“I have-” Blue panted out. ”-another claim growing in my belly.” He wanted Black so bad, and for him to let him finish so bad, but he didn’t want this to escalate into something it couldn’t be. Black could have his body, but his pussy wouldn’t be just his for a few more weeks.

“Did you think I wouldn’t care for them as if they were my own?” Black climbed onto the bed, moving Blue to his hands and knees, giving his hands access mainly to his heavy womb. “Though you will grow my claim as well, once we are ready.”

Blue focused on shaky inhales, he’d forget to breath otherwise.

“As many times as you want.” Oh _stars_ , the thought of being knocked up with Black’s baby put a whole new perspective on pregnancy. He wouldn’t let Blue spend a day alone, much less weeks. Apparently the breasts and size didn’t put him off at all. How many would Black want? At least one, but where did that number top off? Two? Three?

“That’s the correct answer.” Before Blue could ask, Black slid the panties off to the side, and pushed in the tip of his cock. Blue sighed in relief. “Now take it all in.”

The slow push did eventually take all of Black, Blue’s tongue lolled half out from the stimulation. His delicate walls had been untouched for months, (Blue didn’t do toys for solo sessions) and the feeling of a cock gliding inside him was overwhelming.

“Mmmmmmmmmmm.” Blue’s eyes slid shut, lost in pleasure as he was. Black slowly pulled out, just as slowly pushing all the way back in, hands gripping Blue’s hips. He could feel every inch with his heightened sensitivity. Blue didn’t need to say anything, Black continued the even pace without needing a cue other than the delightful sounds from Blue’s mouth.

“We’re going to have so much _fun_.” His hands slid down to his gravid belly. “I’ll admit, my attraction to you has gotten uncontainable in the past few months.”

“I’ve been getting - MWEH - huge during that time,” Blue panted out.

“You’re carrying a baby Blue. It’s _incredibly_ attractive on you.” Black picked up the pace while talking, leaving Blue to just feel overwhelmed and hear nothing else but Black’s words. “You were already adorable, soft smile and cute laugh, but to see you _like this_ , becoming a mother, growing a souling, and all on your own. What a strong mate you’d make, how sexy you’d be all belly and curvy body.” Black finally let out a few grunts, holding Blue by the belly in his obsession. “I didn’t know this would affect me like this, but now that I have you, _I will never let you go_.”

Blue whined from the contact, thrusts ratcheting up to hard, fast. His belly wobbled under the motions, swaying Blue until he felt the beginning of the end.

“BLACK, I’m so close!” Blue tightened around him, earning a very dominant growl in exchange. “P-Please! AHH!”

“Drop down onto your elbows and let it happen.” Black’s hand tightened, but he moved them closer to Blue’s hips. Blue dropped down, Black hitting deeper. His breasts dropped onto the bed, sensitive nipples rubbing up against the sheets and increasing his desperation. His orgasm built from deep in his pelvis, spreading farther and farther until his body exploded under the intensity. Blue couldn’t hold onto more than Black’s name.

And upon hearing and feeling Blue lose it on him, Black growled out his finish.

“You are MINE.” Blue felt Black’s release inside him, whimpering at the idea of being filled when he was already so full. He could feel light bruising by his hips from the Black’s strong grip. 

He fell onto his side when Black pulled out. Black’s cum leaked out of him, but he was too exhausted to stop it. He also noticed the wet spots on the sheets from the leaking nipples.

“Sorry for the mess.” He breathed deeply. He felt like he had run a marathon. It’d been so long.

“How many times must I repeat myself?” Black kissed his head fondly. “You have nothing to be sorry for. Messes can be cleaned. I’d trade a million messes to have you.” He spooned Blue from behind, settling a hand around him over his belly. “Both of you.”

“Love you too Black.” He heard the chuckle, before a clean blanket was pulled over him.

“Now rest, love. We’ll work out the rest in the morning.”

The idea of dealing with Swap, the baby, the everything, felt like such a big undertaking. It’d be nothing but stress, but when he linked hands with Black over the souling, pulsing with joy at this new soul nearby, he knew it’d all work out perfectly fine.

**Author's Note:**

> Written as part of Kinktober.


End file.
